Nano-scale wires such as carbon nanotubes with a very small size scale, on the order of 1-100 nanometers in diameter and 0.1-100 .mu.m in length, have received considerable attention in recent years. See Liu et al., SCIENCE, Vol. 280, p. 1253 (1998); Ren et al., SCIENCE, Vol. 282, p. 1105 (1998); Li et al., SCIENCE, Vol. 274, p. 1701 (1996); Frank etal., SCIENCE, Vol. 280, p. 1744 (1998); J. Tans et al., NATURE, Vol. 36, p. 474 (1997); Fan et al., SCIENCE, Vol. 283, p. 512 (1999); Collins et al., SCIENCE, Vol. 278, p. 100 (1997); Kong et al., NATURE, Vol. 395, p. 878 (1998); and Ebbesen et al., NATURE, Vol. 382, p. 54 (1996).
Carbon nanotubes exhibit unique atomic arrangements, nano-scale structures and interesting physical properties such as one-dimensional electrical behavior, quantum conductance, and ballistic transport characteristics. The ballistic transport in carbon nanotubes, as reported by Frank et al, allows the passage of huge electrical currents in electronic circuits, with the magnitude of current density comparable to or better than those in some superconductors. Carbon nanotubes are one of the smallest dimensioned nanowire materials with generally high aspect ratio. They may have a small diameter of .about.1 nm in the case of single-wall nanotubes and less than .about.50 nm in the case of multi-wall nanotubes. See Rinzier et al, APPLIED PHYSICS, Vol. A67, p. 29 (1998); Kiang et al, J. PHYSICAL CHEM., Vol. 98, p. 6612 (1994), and Kiang et al, PHYSICAL REVIEW LETTERS, Vol, 81, p. 1869 (1998).
High-quality single-walled carbon nanotubes are typically grown as randomly oriented, needle-like or spaghetti-like, tangled nanotubes by laser ablation or arc techniques (a chemical purification process is usually needed for arc-generated carbon nanotubes to remove non-nanotube materials such as graphitic or amorphous phase, catalyst metals, etc.). Chemical vapor deposition (CVD) methods such as used by Ren et al., Fan et al., and Li et al tend to produce multiwall nanotubes attached to a substrate, often with a semi-aligned or an aligned, parallel growth perpendicular to the substrate. As described in these artides, catalytic decomposition of hydrocarbon-containing precursors such as ethylene, methane, or benzene produces carbon nanotubes when the reaction parameters such as temperature, time, precursor concentration, flow rate, are optimized. Nucleation layers such as a thin coating of Ni, Co, Fe, etc. are often intentionally added to the substrate surface to nucleate a multiplicity of isolated nanotubes. Carbon nanotubes can also be nucleated and grown on a substrate without using such a metal nucleating layer, e.g., by using a hydrocarbon-containing precursor mixed with a chemical component (such as ferrocene) which contains one or more of these catalytic metal atoms. During the chemical vapor decomposition, these metal atoms serve to nucleate the nanotubes on the substrate surface. See Cheng et al., CHEM. PHYSICS LETTERS, Vol. 289, p. 602 (1998).
The modern trend in electronic circuit design, interconnection and packaging is toward use of finer features, such that submicron feature sizes have been reached in recent years. To produce desired, ultra-high density electronic packaging, a small width of the circuit lines is important, as well as a three-dimensional, multi-layer configuration with vertically-integrated circuit layers. However, nanowires grown with presently-available methods are not suitable for such purposes. The as-grown single-wall nanotubes (SWNT) such as commonly synthesized by laser ablation or arc method, have a spaghetti-like configuration and often are tangled with each other. The multi-wall nanotubes (MWNT), such as commonly made by chemical vapor deposition, are easier to prepare in an aligned and parallel configuration. However, these as-grown nanotubes such as reported by Ren et al. and Li, et al. differ in height or length. For reliable circuit interconnections without electrical shorts or opens, it is desirable to prepare nanowires having equal and specific predetermined lengths. Co-pending application titled "Article Comprising Vertically Nano-Interconnected Circuit Devices and Methodfor Making the Same," filed concomitantly herewith by inventors Brown, Choi and Jin herein, discloses fabrication approaches for equalizing the length of nanowires and bonding them to circuit substrates for interconnections. However, it also would be advantageous to provide a method for growing the nanowires in-situ between circuit pads or components thereby avoiding equalization and soldering operations.